Related Applications
A patent application, Ser. No. 502,869, co-filed in the name of R. E. Hefner, Jr. as the inventor, with the present application, is directed to the flexibilization of unsaturated polyesters and/or polyesteramides terminated with polycycloalkenyl end groups--such as are deriveable from dicyclopentadiene concentrates, for example.
Another application, Ser. No. 502,886, also co-filed herewith, in the names of P. H. Martin and A. W. Baker as the inventors, is directed to the flexibilization of vinyl ester resins, i.e., of resins comprising vinyl esters deriveable by adduction of monomeric, vinyl-reactive carboxylic acids with the oxirane groups in various types of epoxy resins.
Unsaturated polyester resins are well-known compositions of many uses. The voluminous literature on polyesters is summarized in Vol. 18 of the Encyclopedia of Chemical Technology (Kirk-Othmer; 3d ed.) at pages 575-594. More recently developed but also well known and highly useful are the unsaturated polyesteramide resins. (The "resins" referred to are actually mixtures of the polyester or polyesteramide alkyds with non-resinous vinyl monomers such as styrene.)
It is well recognized that the latter resins could stand improvement in several respects. They typically undergo extensive shrinkage upon curing and the cured resins possess relatively low impact strengths and percent elongations. U.S. Pat. No. 3,448,172--believed to constitute the nearest known prior art to the present invention--discloses substantial improvement in flexural strength and shrinkage of unsaturated polyester resins by adding relatively large amounts of certain "high molecular weight urethane polymers having an ordered arrangement of pendant unsaturation". However, said urethane polymers are relatively complicated to make and--judging from the examples in the patent--the amount of the urethane polymer used must be about equal to the amount of the alkyd component in order to affect the claimed improvement.